This invention relates to lubrication systems for internal combustion engines. Such engines have been established for over 100 years, and there has been no fundamental change to their lubrication system over the years. Thus, it is traditional to provide an oil lubrication system in which a separate oil pump is provided for circulating the oil to the various moving parts thereof.
An object of the invention is to provide a lubrication system in which oil is circulated without the need for a separate oil pump.
According to the invention, in an internal combustion engine including a crankshaft and an associated oil sump, a camshaft in a cylinder head above the oil sump, and a timing belt connecting these shafts via respective pulleys, the timing belt is adapted to entrain a sufficient quantity of oil from the oil sump to lift it to the cylinder head for lubricating purposes.
Conveniently, oil is returned to the sump via an oil cooler, to enable the entrained oil to be used additionally for cooling purposes.
As known per se, the camshaft and crankshaft pulleys have similarly formed tooth sets, but are of different diameters to effect the timing required, and the timing belt is of an impermeable material over its width and formed with a set of teeth around its inner face for meshing with said toothed pulleys.
In accordance with a feature of the invention, an additional oil pulley is provided immersed in oil within the oil sump, and below the level of the crankshaft pulley, the oil pulley also being toothed and the timing belt having an additional set of teeth extending around its outer face for meshing with the teeth of the oil pulley, said outer teeth providing the means for entraining oil to the cylinder head.
In one form, the additional set of teeth may be formed with scoops for entraining the oil.
Preferably, the additional teeth are designed to run closely within a closed passage, whereby they act with the wall of the passage to entrap and entrain the oil.
According to another aspect of this invention an engine lubrication system includes a toothed pulley, the teeth of which run over a part of the rotation within a restricted passage and a belt having matching teeth which also runs for part of its movement within a restricted passage, these runs being guided to a meshing point at which oil under pressure as a result of the meshing action is available.